Pouch containers of indeterminate shape which are capable of varying shape (hereinafter referred to as "pouches") have been increasingly utilized in various fields in recent years because they can be stored conveniently and discarded easily after use. The pouches of this type have a plug fitted with a screw type cap for the purpose of facilitating the entry therein and the exit therefrom of a liquid and allowing the preservation therein of a remaining part of the liquid. This plug is in the shape of a long cylinder having one terminal side thereof inserted into the interior of the pouch and the other terminal side thereof projected out of the pouch for the purpose of preventing the pouch from being folded and securing a flow path for the liquid. Since these pouches are prone to vary volume, they are charged with a liquid by means of a metering packing machine.
Plugs intended for use in the pouches of this type have been proposed in various patent publications. For example, a plug using a pipe provided as extended into a pouch and provided at the leading end thereof and at the fitting part thereof with openings was proposed in Japanese Utility Model publication (examined) Hei. 2-21399, a plug using a pipe disposed as extended into a pouch and provided in the pipe with a plurality of througholes was proposed in Japanese Utility Model publication (examined) Hei. 5-44294 , and a plug using a pipe disposed as extended into a pouch and splitting this pipe thereby forming interstices in the pipe was proposed in Design Registration No. 814883.
The plugs which are used for the pouches described above are required to fulfill various conditions such as allowing easy extraction of the air entrapped in the pouch before the pouch is filled with the liquid, allowing easy extraction of the liquid from the pouch without leaving behind a residue thereof in the pouch, and not allowing the plug to slant when the pouch is filled with the liquid (with a view to enhancing ease of handling and improving appearance). Despite this fact, the plugs which have been proposed in the patent publications mentioned above they encounter difficulty in wholly satisfying such various conditions as mentioned above.
Specifically, the plug proposed in Japanese Utility Model publication (examined) Hei. 2-21399 is incapable of thoroughly extruding the liquid stagnating in the periphery of the middle part of the pipe because of the length of the pipe extending into the pouch, and the plug proposed in Japanese Utility Model publication (examined) Hei. 5-44294 not only suffers incapability of attaining thorough extrusion of the liquid stagnating around the pipe and in the plurality of through holes but also incurs high cost because of the complexity of shape. Further, since these plugs both occupy large volumes relative to the inner volumes of their respective pouches, they cause considerable amounts of liquid to persist therein and compel their pouches to suffer from poor efficiency of liquid retention. The plug proposed in Design Registration No. 814,883 exhibits only inferior strength and possibly deforms while the pouch is being charged with a liquid heated to an elevated temperature. Further, when these plugs are randomly piled up and handled by means of an automatic aligning device, they have the possibility of inconveniencing the aligning operation by suffering the leading ends of some of the pipes of the plugs to be nipped between the openings in the other pipes.